The present invention is related to use of high-intensity, typically pulsed, broadband or deep ultraviolet wavelength electromagnetic radiation for providing non-chemical flux enhancement and virus kill in microfiltration hollow-fiber membrane water treatment.
Current water purification technologies, including distillation, reverse osmosis, and carbon filtration usually produce suitable water quality, but their high capital, operating and maintenance costs have limited their use to only those situations where water shortages are most extreme or where cost is less important. Water contaminated with pesticide or gasoline contaminants are especially difficult and costly to remove with conventional technologies.
Both advantages and disadvantages of the prior art technologies are summarized below:
Vapor compression (VC), including distillation technology systems are used on drinking water for both pathogen and chemical contamination remediation, remove total dissolved solids (TDS) and are excellent for desalinization. Drawbacks include a relatively high price, a generally large size, non portability and fairly complex construction and operation.
Reverse Osmosis (RO) removes TDS with a relatively simple mechanism. Removal of non-volatile organics, pathogen is easy. However, the systems are subject to contaminating product water if feed water pressure and turbidity are out of operating parameters, involve a high price rate, does not remove dissolved organic compounds and are complex and sophisticated.
Air stripping (AS) is generally the least expensive form of water remediation and is fairly good at removing volatile organics. However, these systems are also large, very noisy and unsightly, do not remove non-volatile organics, do not remove pesticides or pathogens, depend on ancillary technology, like the use of granulated activated carbon (below), resulting in more OandM cost as well as air pollution (the volatile organics are transferred into the atmosphere).
Granulated activated carbon (GAC) are effective at removing volatile and non-volatile organics like pesticides, is likewise effective at removal of pathogens, and can be reactivated in most cases. However, GAC also requires resupply of heavy, bulky material, typically has a large adsorption ratio, such as about 1000 pounds GAC to 1 pound contaminant, and itself becomes a source of contamination of product water if allowed to saturate. Furthermore, saturated GAC is a hazardous waste product and must be handled as such, especially when considering issued including transportation, disposal or reactivation cost.
Low and medium pressure mercury vapor ultraviolet (UV) radiation is also effective at destroying or inactivating pathogens, but only very slightly effective on organic or synthetic organic compounds at practical flow rates. Sometimes UV is used as part of a polishing loop on larger treatment systems. However, as a practical matter, use of UV radiation in the past has been impossible. These systems are not practical for treating chemically contaminated water, the available low pressure lamps are typically not self cleaning, would require hundreds of lamps to equal the dosage of a lamp of the present invention, and provide a larger footprint for any type of alternative remediation application.
Mercury lamps emit wavelengths from excited mercury, though not in a smooth arc continuum like the radiator of the present invention, but rather in discrete xe2x80x9catomic linesxe2x80x9d that have very narrow bandwidths. Most of the energy is contained in the 254-nm line with lesser amounts in the 185-nm and 365-nm lines. Mercury lamps also produce especially in the case of medium pressure mercury lamps a low emissivity continuum. That is, a very small level of xe2x80x9cbackgroundxe2x80x9d UV that spans from 185 nm to 400 nm.
Ozone saturation is effective at reducing counts and effects of pathogens and leaves no dangerous chemicals in the water. However, providing a system which injects ozone into a water supply or stream leaves physically a rather large footprint, i.e., requires a larger operation to achieve equivalent effect, is complex to build and operate, involves high operation and maintenance costs, involves the production of ozone a dangerous and reactive gas, and is not practical or feasible for treatment of chemical contaminants alone.
Finally, the use of chlorine (Cl) is known to act aggressively against pathogens but has few remedial effects on chemical contaminated water except for elimination of cyanides. Current competing technologies for chemical contamination of groundwater include reverse osmosis (RO), air stripping, and Activated Carbon filtration. Although the popularity of RO has gained substantially in market share in recent years, different technology solutions continue to dominate the various niches. RO membrane production is dominated by a few companies (DuPont, Sow-Filmtec, Fluid Systems, Toyoba, etc.), but there are thousands of companies that act as integrators of RO systems. Air stripping is older technology and lower cost, but is noisy, unsightly, pollutes the air, and has limited effectiveness in removing MTBE to current and foreseeable EPA standard levels. Activated Carbon filtration involves large quantities of carbon supplied by companies like Calgon, Inc.
Pathogen removal from drinking water is sometimes accomplished with the addition of chlorine, distillation techniques, or the use of banks of low or medium pressure ultraviolet lamps. Distillation suppliers include large European, Japanese, and Korean manufacturers and contractors, and this technology excels at the removal of TDS (total dissolved solids). Current ultraviolet lamp suppliers include Aquafine, Fisher and Porter, and Puress, Inc. There exists a need for technology which is more energy efficient and can simultaneously remove, inactivate or destroy pathogenic and chemical contamination. Such equipment could also be used for post-treatment at desalination facilities to remove chemical contaminants.
Traditional UV technology relies on low and medium pressure UV lamps, similar to the fluorescent lamps used in office buildings. Medium pressure lamps are operated at higher power levels than the low pressure lamps and, consequently, are slightly more efficient than the standard low-pressure variety. The typical low-pressure lamps operate in a range from about 30 to about 100 watts while the medium pressures radiators average about 3000 watts. Typically, both lamp types are known as atomic line radiators. They produce light energy in very narrow wavelength bands at 10-20% electrical efficiency. Both types operate with AC-type current and are controlled by electrical ballast.
Though the lamp life is generally very long, maintenance cost are generally very high, especially in the case of low-pressure lamps. Cleaning is a significant problem. Lamps become fouled in the water environment from precipitated dissolved solids and xe2x80x9cscumxe2x80x9d. This fouling action gradually reduces the UV output rendering the individual lamp wholly or partly useless. Therefore, these lamps must be removed on periodic bases and manually cleaned. Furthermore, low- and medium-pressure lamps do not produce the radiative power levels to effectively dissociate the chemical bonds of many common types of contaminants. They find their principle usage in the wastewater reclamation industry for biological degradation. At a single installation, these lamps are used hundreds and sometimes thousands at a time, thus amplifying the operating and maintenance (OandM) costs.
Improvements to this type of technology include: enhanced chemical doping of the glass used in the envelope of the lamp to increase its UV conversion efficiency, improved cold cathodes to prolong lamp life and improved reaction chambers or effluent channels to maximize dosage and throughput and to minimize head loss.
U.S. Pat. No. 5,891,399 issued to Owesen teaches a device, used in an air purifying system. The device includes an Ultraviolet (UV) radiation source, a pre-filter, and a post-filter.
U.S. Pat. No. 5,312,534 issued to Liboff et al. teaches a method and apparatus for enhancing the transport of a selected ion having a predetermined charge-to-mass ratio through a biomolecular membrane located in a space subjected to a local magnetic field.
U.S. Pat. No. 5,652,050 issued to Pall et al. teaches melt-blown fibrous webs having a uniform structure for use in processing biological fluids such as blood, urine, and saliva, particularly useful for separating plasma or serum from blood.
U.S. Pat. No. 5,238,581 issued to Frame et al. presents a method of enhancement of oxidation of complexed cyanide using oxygen as the oxidizing agent when certain metal chelates are used as catalysts, to reduce the cyanide concentration in aqueous streams arising from complexed cyanide. The enhancement is achieved by irradiating the complexed cyanide with ultraviolet light prior to or concurrent with the oxidation. The oxidation can be performed heterogeneously, especially in a continuous fashion using a packed bed reactor, by using suitable water-insoluble metal chelates, when supported on appropriated carriers.
U.S. Pat. No. 4,846,978 issued to Leggett et al. teaches an improvement in the process which destroys the metal chelate by ozonation to decontaminate the waste streams. The addition of magnesium hydroxide to the solution containing the metal chelates prior to ozonation permits more effective and faster decomposition of the chelates.
U.S. Pat. No. 4,849,114 issued to Zeff et al. describes an improved method of treating halolgenated or partially oxygenated hydrocarbons in aqueous solutions by using in combination, ozone, hydrogen peroxide and ultraviolet radiation simultaneously. The addition of hydrogen peroxide to the UV/ozone combination results in a greatly increased efficiency of oxidation, particularly for compounds which are resistant to oxidation by ozone and UV.
U.S. Pat. No. 5,741,427 issued to Watts et al teaches a system for treating contaminants in an in situ environment in which an oxidizing agent and a unique reagent comprised of a reaction product complex formed from the reaction of a ligand donor and a metal catalyst is provided to the in situ environment to thereby reduce or eliminate contaminants present therein.
U.S. Pat. No. 5,688,378 issued Khoe et al teaches a process for the photoassisted oxidation of dissolved species such as arsenic, iron, phosphorous and sulphur by supplying to a solution including the species to be oxidized an oxidant and a photoabsorber, and then irradiating the resultant solution with UV/electromagnetic radiation. The resulting oxidized species can then be subsequently treated, used or removed through precipitation.
U.S. Pat. No. 5,837,142 issued to Mullerheim et al describes a method and apparatus for treating sanitary wastewater using membrane filtration. The system separates wastewater into liquid and concentrated solid components by membrane separation. The liquid component is discharged or reused as is, or is further treated to render it disposable or reusable for particular applications. Alternatives for treating the liquid component include deodorization and biological stabilization by ultraviolet radiation and ozonation.
U.S. Pat. No. 5,607,593 issued Cote et al teaches an installation for the treatment of potable water including a reactor with a treatment chamber, a plurality of filtration membranes laid out within the chamber, and an ozone injection assembly.
U.S. Pat. No. 5,215,633 issued to Liboff et al. teaches a method for enhancing the transport of a selected ion having a predetermined charge-to-mass ratio through a biomolecular membrane located in a space subjected to a local magnetic field.
The present invention combines emerging technologies of pulsed blackbody ultraviolet light integrated with hollow-fiber microfiltration membranes to provide advanced municipal and industrial water treatment.
The present invention comprises a system and method for enhancing the flux and separation properties of water filtration membranes by oxidizing raw or processed water constituents with direct photolysis of the water matrix by pulsed blackbody UV, yielding ozone and hydrogen peroxide, hydroxyl radicals and other short lived oxidizing species. The result is precipitation of inorganic molecules or organically complexed minerals, partial or complete mineralization of organic molecules and the deactivation or destruction of microbes including: virus, bacteria and protozoa thereby enhancing the overall flux or flow of water through the individual membranes.
The system and method for enhancement of water flux through a filter membrane comprises a UV reactor having at least one treatment chamber, the reactor having an assembly to convey the water to be treated into the chamber; a filter assembly such as a filtration membrane to screen the UV treated water; an optional caustic supply means for the post-treatment of water; and a recovering assembly for recovering the permeate at an outlet of the filtration membrane or other means.
The effect of such UV water treatment prior to ultrafiltration or other filtration is multifaceted. One important and valuable aspect of the present invention is the reduction of the transmembrane pressure (TMP), that it, the pressure drop of the water across the membrane. Another benefit of the present invention is the reduction in the backwash and caustic cleaning cycle times, concentrations and pressures required. The oxidation of iron and manganese to insoluble compounds, without the addition of oxidizing agents, does not harm the membranes. Iron and manganese turn into hydroxide crystals trapped by the filtration membrane and separated from the permeate. Such UV treatment prevents the formation of a biofilm on membrane by reducing the microbes by reducing their food source, namely organic compounds thereby leading to reduced TMP. These effects integrate to enhance the water flux through the filter membrane, cartridge or other filter means.
Thus, it is an object and an advantage of the present invention to provide a method which requires a drastically reduced operating footprint. It would be desirable to provide one lamp which can provide the same dosage that would take hundreds of mercury UV lamps and can do so more efficiently since most (80%) of the blackbody radiation spectrum from the lamp is used. In contrast, the mercury lamps of the prior art produce a very narrow bandwidth of usable UV energy with an energy efficiency of only about 15-20%.
Another object of the present invention is to provide UV blackbody radiation that ranges from about 750,000 to about 9 million overall watts of broadband primarily deep UV radiative power produced at average power inputs ranging from about 2,500 watts to about 18,750 watts per lamp. These power output levels would easily provide enough energy per pulse to dissociate chemical bonds and a sufficient number of pulses per second would sustain the free radical chain reaction or reactions necessary to oxidize/reduce the contaminants present.
Another object and advantage of the present invention is to provide thousands of times more dosage to destroy pathogens, at a lower energy cost, than the standard, currently marketed, UV technology.
Another object of the present invention is to provide a unique reaction chamber design that overcomes the problems of light absorption based on water quality. In this way, water that has a high level of dissolved solids, that would normally absorb light energy, can be used without any extra filtering or pretreatment.
Another object and advantage of the present invention is to provide a system that can be produced inexpensively, resulting in lower capital cost per unit. Another object of the present invention is to provide a system which requires low operation and maintenance costs. Such systems would operate automatically with minimal maintenance.
Another advantage of the present invention is to provide high intensity broadband radiation to provide the absorption wavelengths necessary for disruption of, essentially and effectively, all organic bonds, resulting in high efficiency organic bond dissociation, with as much as or more than 80% of the total light energy generated to oxidized the constituent contaminants.
One object and advantage of the UV water treatment of the present invention is the reduction of the transmembrane pressure (TMP).
Another object and advantage of the present invention is to provide a system with reduced required backwash and caustic cleaning cycle times, volumes and concentrations.
Another object and advantage of the UV water treatment is the oxidation of iron and manganese to insoluble compounds without the addition of oxidizing agents, which can harm the membrane. The filtration membrane is now able to trap iron and manganese and separate them form the permeate.
A further object and advantage of the present invention is the prevention of a biofilm formation on the membrane by reduction of the microbes and the reduction of their food source, namely organic compounds; leading to reduced TMP.
A further object and advantage of the present system is that it is non-chemical, compact and cost effective and preconditions water to pass through a microfilter.
All these benefits enhance the flux of water through the membranes, leading to cost reductions and overall increased water treatment system efficacy.